Method and apparatus for controlled reaction in a reaction matrix

ABSTRACT

Method and apparatus are provided for establishing and controlling the stability and movement of a reaction wave of reacting gases in a matrix of solid heat-resistant matter. At least a portion of the bed is initially preheated above the autoignition temperature of the mixture whereby the mixture reacts upon being introduced into the matrix thereby initiating a self-sustaining reaction wave, after which, the pre-heating can be terminated. The stability and movement of the wave within the matrix is maintained by monitoring the temperatures along the flowpath of the gases through the bed and adjusting the flow of the gases and/or vapors or air to maintain and stabilize the wave in the bed. The method and apparatus provide for the reaction or combustion of gases to minimize NO x  and undesired products of incomplete combustion.

FIELD OF THE INVENTION

The present invention is directed to a method and apparatus for thecontrolled reaction, and in particular for combustion, of gases orvapors within a bed matrix whereby the stability and movement of thereaction wave is controlled to minimize or eliminate undesirableemission products such as NO_(x) and products of incomplete reactionsuch as CO and hydrocarbons.

BACKGROUND OF THE INVENTION

Many process streams of vapors, such as effluents from chemicalprocessing plants, refineries, etc., utilize combustors to destroy thegases or vapors prior to release to the atmosphere. However, withincreasing demands on environmental control of emissions, the use offree flames to combust such effluents is in many cases unsatisfactory. Afree flame also results, in some instances, in incomplete combustion anduncontrollable production of undesirable side products. The presentprocess and apparatus provide a method for controlling and stabilizingthe reaction wave, which is flameless, in which the gases are reactedwithin a controlled area of the matrix at substantially uniform andrelatively low temperatures. The uniformity of the reaction waveprovided by the present invention, and the increased mixing and heattreatment afforded by the matrix according to the present invention,provide for a high conversion of reactants to products. Moreover, thisconversion may be obtained at lower temperatures and residence timesthan those required in a conventional incinerator. There is alsoinherent safety in the use of a process in which there are no openflames, and in which the mixture of gases to be introduced into thematrix is relatively cool, outside the flammability limits of theconstituents, and therefore, not explosive under ambient conditions.

It is therefore an object of the present invention to provide a methodand apparatus for flameless oxidative reaction of gases or vapors tominimize or reduce NO_(x) emission and products of incompletecombustion.

It is yet a further object of the present invention to provide anapparatus producing a stable, yet controllably movable reaction(combustion) wave in a matrix without the use of catalytic materials.

It is a further object of the present invention to provide a method andapparatus for the destruction of gases and vapors, or the combustion offuel, such as natural gas or organic vapors, whereby the input mixtureof gases may be outside the explosion limit of the constituents.Exemplary compounds include, hydrocarbons, oxygenated hydrocarbons,aminated hydrocarbons, halogenated compounds, and sulfur-containingcompounds.

It is yet another object of the present invention to provide a methodand apparatus for the minimization of thermal- and fuel-NO_(x)combustion by-products to levels substantially below those achievable byconventional combustion technologies such as premixed, nozzle-mixed, orstaged burners, or by NO_(x) removal processes such as ThermalDe-NO_(x), Selective Catalytic Reduction, and Rap-Re-NO_(x).Additionally, the present invention allows for minimization orelimination of nitrous oxide (N₂ O) and ammonia (NH₃), which are oftenby-products of the NO_(x) removal techniques.

The present process and apparatus provide a method for controlling andstabilizing the reaction or combustion of gases within a solid matrix,whereby the reactions occur without any definable flame, but ratherwithin a reaction wave in a controlled area of the matrix, at asubstantially uniform temperature.

These and other objects will be apparent from the following description,appended drawings, and from practice of the invention. The followingdescription will be made in conjunction with reactions describingcombustion, such as combustion of natural gas, but the present inventionis not limited to the combustion of gases with the object of minimizingNO_(x) and other products of incomplete combustion. The controllabilityand versatility of the method and apparatus according to the presentinvention also provide, if desired, the ability to synthesize NO, CO,hydrocarbons, or selected products of incomplete combustion, forexample, by varying the outlet temperatures of the reactor, inletcomposition of the stream, the residence time of the stream within thereactor, stream heating value, etc.

This method and apparatus can be functionally applied to processes wherethe minimization of NO_(x) and PICs (products of incomplete combustion)is desired in conjunction with either (a) destruction of a particulargas or vapor, or (b) combustion of fuel to generate heat.

SUMMARY OF THE INVENTION

The present invention provides a method for establishing, maintainingand controlling the stability and movement of the reaction wave of thereaction of gases or vapors comprising the steps of directing a mixtureof the gases or vapors, with air and/or oxygen, into a bed of solidheat-resistant matter, at least a portion of the bed initially beingabove the autoignition temperature of the mixture, whereby the mixtureignites and reacts exothermally in the bed, forming the reaction wave.Within an appropriate range of inlet mixture compositions, the reactionis self-sustaining; no external heat being required to maintain theprocess temperature. The location and stability of the reaction wave ofthe reacting mixture within the bed is controlled by monitoring thetemperatures along the flowpath of the mixture through the bed andadjusting the flow of gases or vapors, and air or oxygen to maintain andstabilize the reaction wave. The invention provides an apparatus forutilizing this method comprising a bed of solid heat-resistant matter,which bed may be insulated to the exterior environment; means forintroducing the gases or vapors into the bed, means for mixing the airor oxygen with the gases, and means for controlling the volume and/orflowrate of the gases and vapors, air or oxygen into the bed. Theapparatus will also have means for monitoring the temperature at one ormore points along the flowpath of the gases in the bed, means foradjusting the flowrate and/or volume of the gases in response totemperature changes in the bed and means for exhausting the products ofcombustion from the bed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of a preferred apparatus for use inaccordance with the present invention.

FIG. 2 shows the hot and cool zones in the apparatus of FIG. 1 duringoperation.

FIG. 3 is a second preferred apparatus for use in accordance with thepresent invention.

FIG. 4 is yet another preferred apparatus for use in accordance with thepresent invention.

FIG. 5 is another configuration of a preferred apparatus in accordancewith the present invention.

FIG. 6 is a variation of the apparatus of FIG. 5.

FIG. 7 is another variation of a preferred apparatus of the presentinvention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The apparatus according to the present invention contains a bed ofheat-resistant material and means for monitoring the temperature alongthe flowpath of gases through the heat-resistant material. By monitoringthe temperature of the reaction wave within the bed matrix andcontrolling the flow and/or volume of gases entering and leaving thematrix as well as the temperature of the matrix, the reaction wave maybe maintained at a relatively uniform temperature radially and at aconstant location within the bed. The reaction matrix bed may be sizedfor any desired flow stream by altering the matrix flow cross-section,height, material, void fraction, outlet temperature, and supplementalheat or fuel value addition, if desired. Preferred matrix materials areceramic balls, but other bed materials and configurations may be used,including, but not limited to, other random ceramic packings such assaddles or pall rings, structured ceramic packing, ceramic or metalfoam, metal or ceramic wool and the like. By maintaining the stabilityand uniformity of temperature of the reaction wave within the matrix,and as a result of the fundamentally enhanced reaction wave propagationmechanism of inner body surface radiation coupled with forced convectionand inner matrix solids thermal conduction, it is believed that thematrix burning velocity of the mixture in the matrix may be independentof, or more independent of the system pressure than the burning velocityof an identical mixture by conventional incineration. This is animprovement over conventional combustors wherein the laminar flame speedof fuel mixtures in air decreases significantly with increasing systempressure. See "Laminar Flame Speeds of Methane-Air Mixtures UnderReduced and Elevated Temperatures", Egolfopoulos, F. N., et al.,Combustion and Flame, Vol. 76, 375-391 (1989). According to the presentinvention, the combustion intensity of reacting gases through a unitcross-sectional area would increase directly with pressure, since themass flow of gases would increase directly with pressure, and the matrixburning velocity is not expected to decrease with pressure. Thenon-negative dependence of matrix burning velocity on pressure isexpected to be a result of one or both of the phenomena of in-matrix,backward-propagating, inner-body surface radiation of heat, andforced-convection of heat from the solid matrix to the incoming gases.

The radiative heat transfer within the bed, the walls of the combustorcontaining the bed, and the gas molecules within the reactor themselvesare important features of the operation of the apparatus and the methodof the present invention. Therefore, the types of materials in the bedmay be varied so that the inner body heat transfer characteristics; theradiative characteristics, the forced convective characteristics, andthe inner matrix solids thermally conductive characteristics, may becontrolled within the bed. This may be done by varying the radiativeheat transfer characteristics of the matrix by using different sizes ofbed materials to change the mean free radiative path or varying theemissivity of the bed materials, varying the forced convection heattransfer characteristics of the matrix by varying its surface area perunit volume, or geometry, varying the inner matrix solids thermallyconductive heat transfer characteristics of the matrix by using bedmaterials with different thermal conductivities, or changing the pointto point surface contact area of the materials in the bed. Theseproperties may be varied either concurrently or discretely to achieve adesired effect. In addition to changing the properties of the reactionmatrix itself, an interface or several interfaces can be introduced intothe bed where one or more of the heat transfer properties of the bed arediscretely or concurrently changed on either side of the interface andwherein this variation serves to help stabilize the wave in thatlocation and acts as a "reaction wave anchor." This may be done, forexample, by introducing an interface where void fractions change acrossthe interface within the bed. The interface may change the mean freeradiative path across the interface independent of the void fraction. Bychanging materials, the emissivity may change across the interfacewithin the bed. Changing the area per unit volume of the bed mediaacross an interface, the forced convective heat transfer characteristicsmay change as the gas is passed across the interface.

The matrix cross-section perpendicular to the flow axis may beconfigured in a circular, square, rectangular, or other geometry. Thearea of the cross-section may be intentionally varied (i.e. as atruncated cone or truncated pyramid) to achieve a wide stable range ofreactant volumetric flowrates at each given matrix burning velocity.

The preferred materials of the bed matrix are preferably ceramic ballsor other types of random heat-resistant packing. To evenly distributeincoming gases there will typically, but not necessarily, be a plenum,preferably made of a heat-resistant material such as brick or ceramicballs, in which incoming gases will be preferably distributed andfurther mixed prior to entering the bed. If a plenum of brick or ceramicballs is used, it will typically comprise a section with very low radialpressure drop, so that cross-sectional gas distribution is maximized,and also cause a slight pressure drop (approximately 1/4" to 10" W.C.)across the plenum interface prior to the bed in order to more evenlydistribute the gases entering the bed. In addition, the plenum mayprovide an interface, with varying heat transfer characteristics oneither side of the interface, in the junction between the plenum and thebed. The exterior reactor walls contain the process flow duringoperation, and are preferably made of carbon steel. The exterior wallsmay be lined with a non-permeable, corrosion-resistant coating and arefractory insulating material, such as firebrick, which may be coatedwith a porosity-reducing compound. Dense castable refractory materials,backed up with insulating refractory materials, such as ceramic fiberboard and ceramic fiber blanket, are also preferred lining materials. Tobring the gases and/or matrix up to the desired temperature prior tostarting the reactor, preferably a preheater may be utilized to preheatthe packed bed matrix. Convenient means for mixing the gases and/oroxygen prior to entering the bed may be utilized such as, a venturi-typegas-air mixer. An outlet will be provided, usually at the opposite endof the processor from the inlet, to allow for gases to escape duringpreheating and/or processing. Temperature sensing means such asthermocouples will be located usually in thermowells inserted into thebed. Usually there will be thermowells located at inlet and outlet portsand in the void spaces in the bed.

A programmable control system may be utilized using the outputs from thethermocouples to automatically adjust the dilution air and/orsupplemental fuel to maintain the stability and location of the reactionwave within the bed. Due to the inherently stabilizing thermal mass ofthe matrix, the reactant gases may be introduced in a continuous orintermittent manner.

For a reactor which processes corrosive gases such as chlorine, hydrogenchloride, sulfur dioxide and others, the steel shell may be maintainedat moderately high temperature, preferably 300° to 400° F., to minimizedewpoint corrosion. In addition, the carbon steel shell may be linedwith dewpoint corrosion resistant materials, such as Fortress HighTemperature Stalastic bitumastic coating (Witco). A porosity-reducingcoating, such as Alundum Patch Primer (Norton) on the refractory surfacemay also reduce the permeation of corrosive agents from the interior ofthe processor to the carbon steel shell. The interior temperature of thereactor may typically be maintained between 1400° and 3500° F.,depending on the process requirements. In a typical process, a preheateris used, fired for example with natural gas, to heat the plenum, ifpresent, and the bed in order to raise the bed temperatures above theautoignition point of the gases which will be used. The pre-heater canbe any device which will raise the temperature of the bed directly orany device to pre-heat gases which can then be channeled into the bed topre-heat the bed itself. Pre-heating devices include: gas burners,electric heaters mounted exterior to or interior of, the matrix,inductive heaters, radiant tube heaters, etc. Once a sufficienttemperature has been achieved throughout the entrance portion of theprocessor, preheating is then ceased. Ambient air is then forced withpressure into the plenum, if used, and into the bed until the plenum iscooled to a temperature below the autoignition of the process gases tobe introduced. By introducing ambient air through the plenum, the plenumcools the quickest, while the matrix temperature remains largely abovethe autoignition temperature although the matrix immediately adjacent tothe plenum will be cooled below the autoignition temperature. Once thisprofiling of the bed has been completed, the process gas is introducedinto the plenum, if used, and the bed. The combustion wave isestablished in the matrix whereby the compounds are ignited and oxidizedto stable products, such as water and CO₂. The combustion wave isobserved as a steep increase in bed temperature from ambient temperatureon the inlet side of the wave to approximately the adiabatic flametemperature of the mixture on the outlet side of the wave. This rapidchange takes place over a distance of usually several inches in atypical pilot processor, with the actual distance being dependent uponfeed concentrations, feed rates, gas velocity distribution, bedmaterial, and bed physical properties, type of specific feed materials,etc. Heat losses in the direction of flow also will have an effect onthe length of the combustion wave. The wave may be moved with, againstor stationary relative to the inlet feed direction by varying the feedgas concentration or flowrate. If necessary, heat may be added to orremoved from the incoming gases to further stabilize the wave. Ifdesired, cooled surfaces such as water-containing pipes may be insertedinto or around the matrix to remove heat from the reacting gases andfurther stabilize the reaction wave.

While combustion intensities from 191,520 W/m² to 744,600 W/m² have beenachieved at sub-LEL conditions in a pilot unit, it is believed thatcombustion intensities from 7,000 to 1,800,000,000 W/m² are achievablewith this method at non-atmospheric pressures; or for atmosphericpressure applications, combustion intensities from 90,000 to 150,000,000W/m² are achievable.

Preferably a plenum is utilized at the entry of the bed for uniformityof mixing, cross-sectional velocity profiles and temperature of theincoming gases. It is believed that this helps to achieve a relativelyflat cross-sectional profile of the combustion wave perpendicular to thedirection of the flow of the gases through the bed. In some instancesthe plenum may be desirable to achieve the flatness of the cross-sectionof the wave, depending on the configuration of the matrix. While in someinstances a relatively flat cross-sectional profile of the combustionwave may be desirable, this flatness of cross-sectional profile is notnecessary for the device to work, and in some instances a non-flat,spherical, or bullet shaped profile may be desirable, during whichinstances a plenum may or may not be used. In some cases, a gaspermeable barrier may be beneficial to help maintain the mechanicalintegrity of the matrix during operation where high gas velocities orexcessive vibrations occur.

The reaction wave may move or remain stationary relative to the inletflow direction by increasing or decreasing the percentage of fuel in theinlet mixture. For applications where it is desirable to use gasmixtures below their respective flammability limits, the method isfunctional at relatively low fuel concentrations, for example from 2.7to 4.8 volume percent of natural gas in air. For other applications,where the reaction of fuel and oxygen in near- or super- stoichiometricproportions is desired, the method can function at much higher fuelconcentrations, for example from 5 to 25 volume percent natural gas inair.

Alteration of the flowrate and composition of the inlet stream may beused to cause the combustion wave to migrate upstream or downstream,however, this motion is slow due to the large thermal mass of a typicalmatrix. Similarly, unplanned fluctuations in the flowrate and/orcomposition of the inlet stream may also cause wave migration, howeverthis effect may be reversed by one or more counteracting process changesissued by a programmable controller to control valves governingsupplementary fuel and dilution air, in response to changes in sensedtemperatures along the bed.

In a typical processor as described in further detail hereinbelow usingmethane as a feed gas, the destruction and removal efficiency (DRE) ofmethane has been shown to be greater than 99.99%, independent of thelocation or direction of propagation of the wave within the matrix.

The emission levels of thermal-NO_(x) in the same combustor was lessthan 0.007 lb of NO_(x) (as NO₂) per million BTU, and the CO levels havebeen observed to be below the lower detection limit (10 ppm) of the COanalyzer. Typically, levels of nitrous oxide will not exceed 0.3 pp byvolume.

The burning velocity of the reactant gases in the matrix as described infurther detail herein below, even when measured at conditions below theconventional flammability limit of methane in free air, has beenobserved to be as much as 2 to 10 times greater than the fastest knownlaminar flame speed of methane in free air.

While the above-described information has been observed, it iscontemplated that there is no limit, i.e., minimum or maximum flowrateby which the technology may be utilized. Various plenum configurations,if used, may also be utilized for gas distribution in addition to thosedescribed herein in the attached figures. The flow direction is also notbelieved to be critical so that the system may be preheated or fed fromthe bottom up, top down, sideways, fed at alternative points in theprocessor, or the direction of feed may also be alternated.

The preheating means may be electric or any other kind of heating means,and supplemental heating of the process gases may be utilized. Thecombustion wave may also be utilized in conjunction with regenerativeheat recovery or with internal heat recuperation components identical toor similar to those conventionally available for heat recovery systems.While the present invention contemplates bed material without catalysts,a combined inert bed and catalyst may be used to enhance processcharacteristics such as reaction rate, if so desired. However, a primaryfeature of the invention is that the catalyst is not a necessity to theoperative functions of the stabilizing of the combustion wave.

In addition to its use as a stand-alone processing device, the apparatusof the invention may be employed as an add-on to conventional technologyso as to incorporate the benefits of the invention, such as fluctuationdampening capability, etc. The matrix may be appended, for example, tothe outlet of a conventional incinerator to provide an additional marginof safety to handle process fluctuations.

Among the advantages of the present invention is the ability to controland diminish the undesirable products of combustion of typical fuels bycontrolling the stability of the combustion wave within theheat-resistant matrix according to the present invention. For example,the NO_(x) content of combustion of hydrocarbon gases may be lowered towithin the range of about 0.1 to 40 ppm by volume, dry basis, adjustedto 3% oxygen. Similarly, the carbon monoxide content of combustion ofhydrocarbon gases may be controlled to be within the range of about 0.1to 10 ppm by volume, dry basis, adjusted to 3% oxygen. Other products ofincomplete combustion may be controlled to comprise less than about 5ppm of the total gaseous products, by volume, dry basis, adjusted to 3%oxygen. Another advantage is that the process according to the presentinvention is extremely safe in that the gaseous reactants for thereaction (combustion) wave may be maintained, upon entry into thematrix, at or below the lower explosive limit for the gaseous mixture.This lessens the chance of accidental and premature burning orexplosion. Furthermore, the concentration of incoming reactants may bemaintained at or above the upper flammability limits of the mixture ofgases, further adding to the safety features of the invention, or theconcentration of incoming reactants may be maintained between the upperand lower flammability limits of the mixture of gases.

Since the combustion or reaction wave according to the present inventionis maintained within a matrix, rather than an open flame in a chamber orin open atmosphere, many more controls may be imposed upon thecharacteristics of the combustion wave. The objects which comprise theheat-resistant matter in the bed may be selected by size and shape toobtain a predetermined mean-free radiative path in the matrix.Furthermore the materials of the heat-resistant matter may be selectedso that particles may be placed within the bed having appropriateemissivities to obtain a predetermined back heat transfer from theparticles into the combustion or reaction wave, thereby improving thedesirable characteristics and stability of the wave.

One of the characteristics attainable by the present invention is thestabilization of the combustion or reaction wave at feed flowrates, suchthat the velocities of the mixtures of gases entering the wave whencalculated and adjusted to the conditions of standard temperature andpressure, are greater than the laminar flame speed of the mixture at thesame conditions in absence of the matrix. This calculated velocity maybe obtained using the present invention whereby the velocity is about 1to 1,000 times greater than the laminar flame speed, preferably 1 to 50times greater than the laminar flame speed, which therefore allows forgreater throughput of the reaction gases than that of conventionalcombustion. As further demonstration of the improvements attainable bythe present invention, the combustion wave utilizing the presentinvention may be stabilized at feed flowrates such that the calculatedvelocities of the mixtures of gases entering the wave, adjusted toconditions of standard temperature and pressure, are greater than theturbulent flame speed of the mixtures at the same conditions without thematrix. This calculated velocity may be 1 to 1,000 times greater thanturbulent flame speed and preferably 1 to 10 times greater thanturbulent flame speed.

As further demonstration of the improvements attainable by the presentinvention, a combustion wave maintained and stabilized according to thepresent invention may typically be characterized by a heat release perunit cross-sectional area which is higher than the heat release per unitcross-sectional area in a laminar or turbulent flame of an identicalgaseous mixture at identical conditions, in absence of the matrix of thepresent invention. Preferably the heat release per unit cross-sectionalarea for combustion of a typical hydrocarbon gas is 1 to 50 times higherthan that observed in a laminar flame or a turbulent flame of anidentical mixture of gases at identical conditions, in the absence ofthe matrix according to the present invention.

Typically a matrix according to the present invention will comprise aceramic, which may be randomly packed or structurally packed. Preferredrandom packing comprises ceramic balls which may be layered. Generally,for combustion of hydrocarbon gases the ceramic balls are useful if theyhave a diameter from about 1/16th" to 3" in diameter, preferably about3/4" in diameter. Another useful configuration is the use of randomceramic saddles typically from 1/16th" to 3" nominal size, preferablyabout 1/2" to 1.5" nominal size. Such ceramic saddles are well known inthe art and can be obtained from a number of manufacturers, such as theIntalox® saddles sold by Norton Chemical Processes Products of Akron,Ohio.

A ceramic foam material may also be utilized. Typical foam material maybe utilized which has a void fraction of 10 to 99%, preferably 75 to 95%and most preferably about 90%. The pore sizes in any preferred ceramicfoam material will be about 0.1 to 1,000 pores per inch and preferablyabout 1 to 100 pores per inch and most preferably about 10 to 30 poresper inch.

Other shapes of ceramic material may be utilized such as honeycomb shapeceramic.

Instead of a ceramic, the heat-resistant matter used to form the bed mayalso be a metal, which may be randomly packed or may have a structuredpacking.

In a preferred embodiment, a combustion wave of hydrocarbon gases may bestabilized and maintained in a ceramic matrix wherein the combustionwave is characterized by a length scale of greater than 0.1 centimeter,preferably about 2" to 16" and most preferably about 8". In general, acombustion wave according to the present invention is characterized by alength scale of 1 to 10⁹ times the combustion wave length scale of anidentical mixture, combusting under identical conditions, in absence ofthe matrix. Typically a combustion wave according to the presentinvention may be characterized by a length scale of 1 to 10⁶ times thecombustion wave length scale, and most preferably 1 to 1,000 times thecombustion wave length scale of an identical mixture under identicalconditions, in absence of the matrix. A combustion wave according to thepresent invention at least may be characterized by a length scale of 1to 100 times the combustion wave length scale of an identical mixturecombusting under identical conditions in absence of the matrix.

Referring to the figures, FIG. 1 is a schematic diagram of across-section of an apparatus used for practicing the process accordingto the present invention. The apparatus comprises of a processor (10)comprising a matrix (11) of heat-resistant packing material supported atthe bottom by a plenum (12) for distributing the gases as they enterinto the matrix (11). The void (13) over the top of the matrix (11)precedes the outlet (13a) which penetrates the end wall (14) made of adense castable refractory material (14) behind which there is aninsulating layer (15). The product gases exit through the refractory(14) and insulator (15) through the outlet (13a). A dense castablerefractory material (16) also seals the bottom of the processor (10).The sides of the processor (10) are encased with a insulated shell (17),preferably made of steel and lined on the inner surface with anotherinsulating heat-resistant material such as firebrick. The inner surfaceof the steel may be protected by an appropriate corrosion-resistantmaterial. Through the bottom of the processor (10) is an inlet means(18) through which controlled air, fuel and/or process gas is introducedinto the processor (10). If necessary, the fuel or process gas may beheated prior to introduction to processor (10) by applying external heatto the mixed process gas prior to entering the processor (10) throughline (18). The plenum and lower portion of the matrix (11) may be heatedby a suitable preheater (19) which, for example, may pass forced heatedair into the processor (10). At various points in the matrix (11) arelocated temperature sensing devices such as thermocouples (20) fromwhich the output is fed into a microprocessor or programmable logiccontroller (PLC) (21) which in turn controls the input of the fueland/or process gas and control air or heat supply to control theproportions, flow and temperature of the input gases entering throughline (18) into the processor (10).

Referring to FIG. 2, there is shown a schematic of the internaltemperature zones and combustion wave of the processor shown in FIG. 1.Typically, during operation, there will be a cool zone (24) below theuniform oxidation or combustion temperature which is being maintainedwithin the combustion wave. The combustion wave itself (22) will bemaintained in a stable shape and uniform temperature at a locationwithin the matrix; and above the combustion wave (22) will be a hotregion (23). By using temperature sensors (20), the combustion wave (22)may be located within the matrix and moved to a desired point andmaintained to have a desired height by controlling the input end of theprocessor (10).

Referring to FIG. 3, there is shown another configuration of a processorwhich may be utilized according to the present invention. The processor(30) comprises an inlet (31) for introducing process gases and air. Theitem (32) is an inlet for the preburner for preheating the processorsimilar to that shown in FIG. 1. The matrix in this instance comprisessix different areas. Just below the void (33) there is a stack ofceramic saddles (34) extending through a major portion of the height ofthe bed. Below the saddles (34) is a series of layers of ceramic ballsof increasing size. For example, layer (35) may comprise 1/8" diameterceramic balls, layer (36) 3/8" diameter ceramic balls, layer (37) 3/4"diameter ceramic balls, and layer (38) 11/2" diameter ceramic balls. Thebottom layer (39) may comprise, for example, 3" diameter ceramic balls,which are retained within the processor (30) by porous ceramic plugs(39a) and (39b). At the bottom of the bed the gases exit through outlet(40) and/or (41), if used. As shown on the bottom of the processor (30),it is insulated by a layer of brick (42).

In addition, in one embodiment, one or more gas permeable barriers ormembranes (43),(44),(45),(46), and (47), can be utilized to helpmaintain the mechanical integrity of the matrix during operation, forexample, so that adjacent layers of ceramic materials of differing sizesdo not become mixed due to excessive vibration. These barriers ormembranes can be comprised of a variety of material so long as theyallow for proper gas flow.

Referring to FIG. 4, there is shown a processor (50) having a bedconfiguration similar to that as shown in FIG. 3. The top area of thebed comprises ceramic saddles (51) preceded by a series of layers ofceramic balls of increasing diameter, layers (52) through (56),respectively. The bottom layer 56 is retained within the processor (50)by porous ceramic plugs (56a) and (56b). However, in the configurationshown in FIG. 4, the process gas and air are introduced through inlet(57) at the bottom of the processor (50) and the preheated air forpreheating the processor (50) is introduced through inlet (58) alsolocated at the bottom of the processor. Therefore, the gases exit at thetop of the processor (50) through outlets (59) and/or (60), if used. Thebottom of the processor also comprises a layer of insulation (61) suchas brick.

Referring to FIG. 5, there is shown yet another configuration of aprocessor (62). This processor has a brick plenum (63) through whichpass gases which exit outlet (63a) or (63b), if used. Above the bricklayer (63) is a layer of ceramic balls (64) and a second layer (65) ofballs of different sizes than those in layer (64). Finally, there is themajor portion of the bed comprising saddles or ceramic balls (66). Theinlet gases enter through inlet (67) and pass through void (68) beforeentering into the matrix layer (66). Preheated air for preheating theprocessor (62) enter through inlet (69).

Referring to FIG. 6, there is shown the same configuration as shown inFIG. 5 for a processor (70) except that the processing gases passthrough the bed in the opposite direction. Accordingly, the processgases and oxygen are introduced through inlets (71) into a plenum linedwith brick layer (72). The preheated gases enter through inlet (73) froma preburner (not shown). The preheated air may optionally be formed bycombustion in a preburner located on a combustion chamber (74), whichcombustion chamber serves to more uniformly mix the preheated gasesprior to entry into the bed or plenum. The layers of ceramic ballsand/or saddles (75), (76), and (77) are as described in connection withFIG. 5 for layers (64), (65), and (66), respectively. The exit gasesexit through outlets (78) and/or through outlets (79), if used.

Referring to FIG. 7, there is shown a slightly modified version of theembodiment shown in FIG. 4 and described above. Thus, a processor (50)is shown having a bed wherein the top area of the bed comprises ceramicsaddles (51) preceded by a series of layers of ceramic balls ofincreasing diameter, layers (52) through (56), respectively. The bottomlayer (56) is retained within the processor (50) by porous ceramic plug(56a). The gases exit through outlets (59) and/or (60). The bottom ofthe processor (50) also comprises a layer of insulation (61) such asbrick. The preheated air for preheating the processor (50) is introducedthrough inlet (58), located at the bottom of the processor (50). In thisembodiment, however, the process gas and air are introduced to theprocessor (50) through one or more inlet ports (62) spaced along aninjection pipe (63) that projects into the processor (50) through aninlet (57) and is aligned along the gas flow axis of the processor (50).This configuration can be used for staged combustion to further reduceNO_(x) formation.

While embodiments and applications of the claimed invention have beenshown and described, it would be apparent to those skilled in the artthat many more modifications are possible without departing from theinventive concepts herein. The invention, therefore, is not to berestricted except in the spirit of the appended claims.

Claimed is:
 1. A method for establishing and controlling the stabilityand movement of a reaction wave of reacting gases and/or vapors,comprising the steps of(a) directing a mixture of said gases and/orvapors with air and/or oxygen into a matrix of solid heat-resistantmatter, at least a portion of said matrix initially being above theautoignition temperature of said mixture whereby said mixture ignites insaid matrix to initiate said reaction; (b) maintaining a stable reactionwave of the reacting mixture by monitoring the temperatures along theflowpath of said mixture through said matrix and adjusting the flow ofany of said gases and/or vapor, and air and/or oxygen to maintain andstabilize said reaction wave in said matrix.
 2. A method according toclaim 1 wherein said reaction wave comprises a combustion wave.
 3. Amethod according to claim 1 further comprising the adjustment of thelocation of said reaction wave along said flowpath of said mixturethrough said matrix by (a) adjusting the flow of said gases and/orvapors, and air and/or oxygen, or (b) removing from or adding heat toincoming gases and/or vapors, and air and/or oxygen, or both (a) and(b).
 4. A method according to claim 1 wherein said matrix is insulatedto retain heat generated by said wave in said matrix.
 5. A methodaccording to claim 1 further comprising a step of adding heat to saidmatrix and/or to incoming gases to further control stability andmovement of said wave within said matrix.
 6. A method according to claim2 wherein the gaseous products of said combustion wave are characterizedby low NO_(x) content.
 7. A method according to claim 6 wherein saidNO_(x) content is in the range of 0.1 to 40.0 ppm by volume, dry basis,adjusted to 3% oxygen.
 8. A method according to claim 2 wherein thegaseous products of said combustion wave have a carbon monoxide contentin the range of 0.1 to 10 ppm, by volume, dry basis, adjusted to 3%oxygen.
 9. A method according to claim 2 wherein products of incompletecombustion from said combustion wave comprise less than about 5 ppm ofthe gaseous products, by volume, dry basis, adjusted to 3% oxygen.
 10. Amethod according to claim 1 wherein concentrations of incoming reactantsfor said reaction wave are maintained at or below the lower explosionlimit of said mixture.
 11. A method according to claim 1 wherein fuelconcentrations of incoming reactants for said reaction wave aremaintained between the upper and lower flammability limits of saidmixture.
 12. A method according to claim 1 wherein concentrations ofincoming reactants for said reaction wave are maintained above the upperflammability limit of said mixture.
 13. A method according to claim 1wherein said gases and/or vapors comprise a hydrocarbon.
 14. A methodaccording to claim 1 wherein said gases and/or vapors comprise vapors ofan organic liquid.
 15. A method according to claim 14 wherein saidvapors of organic liquids are selected from the group consisting ofoxygenated hydrocarbons, halogenated compounds, aminated compounds andsulphur-containing compounds.
 16. A method according to claim 1 whereinsaid mixture is introduced into said matrix in a continuous manner. 17.A method according to claim 1 wherein said mixture is introduced intosaid matrix in an intermittently varying manner.
 18. A method accordingto claim 1 wherein said reaction wave is maintained in said matrix in aposition whereby stability of said wave is at least in part maintainedby inner-body surface radiation from insulation and/or said materials insaid bed.
 19. A method according to claim 1 wherein said reaction waveis stabilized in a position in said matrix whereby stability of saidwave is at least in part maintained by forced convection between saidmatrix and said incoming gases and/or vapors, air and/or oxygen.
 20. Amethod according to claim 1 wherein the matrix burning velocity of saidmixture in said matrix is maintained or increased upon increase ofpressure within said matrix.
 21. A method according to claim 1 whereinsaid wave is maintained at a uniform temperature along directionsperpendicular to the flow axis.
 22. A method according to claim 1wherein said heat-resistant matter in said matrix comprises objects ofsizes selected to obtain a predetermined mean-free radiative path insaid matrix.
 23. A method according to claim 1 wherein the emissivity ofsaid matter in said bed varies to obtain a predetermined back heattransfer characteristic from said particles into the wave.
 24. A methodaccording to claim 2 wherein said combustion wave is characterized bylack of a flame.
 25. A method according to claim 2 wherein saidcombustion wave is stabilized at feed flowrates such that the calculatedvelocity of the mixture of gases entering said wave, adjusted toconditions of standard temperature and pressure, is greater than thelaminar flamespeed of said mixture at said conditions in absence of saidmatrix.
 26. A method according to claim 25 wherein said calculatedvelocity is 1.0 to 1000 times greater than said laminar flamespeed. 27.A method according to claim 26 wherein said calculated velocity is 1.0to 50 times greater than said laminar flamespeed.
 28. A method accordingto claim 2 wherein said combustion wave is stabilized at feed flowratessuch that the calculated velocity of the mixture of gases entering thereaction wave, adjusted to conditions of standard temperature andpressure, is greater than the turbulent flamespeed of said mixture atsaid conditions in absence of said matrix.
 29. A method according toclaim 28 wherein said calculated velocity is 1.0 to 1000 times greaterthan said turbulent flamespeed.
 30. A method according to claim 29wherein said calculated velocity is 1.0 to 10 times greater than saidturbulent flamespeed.
 31. A method according to claim 2 wherein thetemperature required to initiate and sustain the combustion wave in saidmatrix is less than the autoignition temperature of said mixture atidentical conditions in absence of said matrix.
 32. A method accordingto claim 2 wherein said step of maintaining said combustion wave isperformed by adjusting said flow of gasses to form a wave characterizedby a heat release per unit cross-sectional area which is higher than theheat release per unit cross-sectional area observed in a laminar orturbulent flame of an identical mixture at identical conditions inabsence of said matrix.
 33. A method according to claim 32 wherein saidformed combustion wave is characterized by a heat release per unitcross-sectional area which is 1.0 to 50 times higher than the heatrelease per unit cross-sectional area observed in a laminar flame of anidentical mixture at an identical conditions in absence of said matrix.34. A method according to claim 32 wherein said formed combustion waveis characterized by a heat release per unit cross-sectional area whichis 1.0 to 50 times higher than the heat release per unit cross-sectionalarea observed in a turbulent flame of an identical mixture at identicalconditions in absence of said matrix.
 35. A method according to claim 1wherein said mixture is directed through a plenum prior to entering saidmatrix.
 36. A method according to claim 35 wherein said plenum comprisesone or more layers of random packing material.
 37. A method according toclaim 36 wherein said layers are configured to achieve a pressure dropthrough the layers.
 38. A method according to claim 1 wherein saidmatrix comprises a ceramic.
 39. A method according to claim 38 whereinsaid matrix comprises random packing.
 40. A method according to claim 39wherein said random packing comprises ceramic balls.
 41. A methodaccording to claim 40 wherein said balls are from 1/16" to 3" indiameter.
 42. A method according to claim 41 wherein said balls areabout 3/4" in diameter.
 43. A method according to claim 39 wherein saidrandom packing comprises ceramic saddles.
 44. A method according toclaim 43 wherein said saddles are from 1/16" to 3" nominal size.
 45. Amethod according to claim 44 wherein said saddles are 1/2" to 1.5"nominal size.
 46. A method according to claim 38 wherein said matrixcomprises structured ceramic packing.
 47. A method according to claim 38wherein said matrix comprises a ceramic foam material.
 48. A methodaccording to claim 47 wherein said ceramic foam material has a voidfraction of 10 to 99%.
 49. A method according to claim 48 wherein saidceramic foam material has a void fraction of 75 to 95%.
 50. A methodaccording to claim 49 wherein said ceramic foam material has a voidfraction of about 90%.
 51. A method according to claim 47 wherein saidceramic foam material has a pore size of 0.1 to 1000 pores per inch. 52.A method according to claim 51 wherein said ceramic foam material has apore size of 1 to 100 pores per inch.
 53. A method according to claim 52wherein said ceramic foam material has a pore size of about 10 to 30pores per inch.
 54. A method according to claim 38 wherein said ceramicmatrix comprises a ceramic honeycomb shaped material.
 55. A methodaccording to claim 1 wherein said heat-resistant matter comprises ametal matrix.
 56. A method according to claim 55 wherein said metalmatrix comprises random metal packing.
 57. A method according to claim55 wherein said metal matrix comprises structured metal packing.
 58. Amethod according to claim 1 further comprising the step of preheatingsaid matrix and/or said mixture of gases prior to introduction of saidgases and/or vapors into said matrix.
 59. A method according to claim 58wherein said step of preheating is by a pre-heating burner.
 60. A methodaccording to claim 58 wherein said step of preheating is by an electricheater.
 61. A method according to claim 2 wherein said combustion waveis characterized by a length scale of greater than 0.1 centimeter.
 62. Amethod according to claim 61 wherein said combustion wave ischaracterized by a length scale of 2 to 16 inches.
 63. A methodaccording to claim 62 wherein said combustion wave is characterized by alength scale of about 8 inches.
 64. A method according to claim 2wherein said combustion wave is characterized by a length scale of 1.0to 10⁹ times the combustion wave length scale of an identical mixture,combusting under identical conditions, in absence of said matrix.
 65. Amethod according to claim 64 wherein said combustion wave ischaracterized by a length scale of 1.0 to 10⁶ times the combustion wavelength scale of an identical mixture, combusting under identicalconditions, in absence of said matrix.
 66. A method according to claim65 wherein said combustion wave is characterized by a length scale of1.0 to 1000 times said combustion wave length scale of said identicalmixture.
 67. A method according to claim 66 wherein said combustion waveis characterized by a length scale of 1.0 to 100 times said combustionwave length scale of said identical mixture.
 68. A method according toclaim 17 wherein said mixture is introduced into said matrix withintermittently varying composition of one or more constituents.
 69. Amethod according to claim 17 wherein said mixture is introduced intosaid matrix with intermittently varying inlet temperature.
 70. A methodaccording to claim 17 wherein said mixture is introduced into saidmatrix with intermittently varying flowrate.
 71. A method according toclaim 1 wherein said reaction wave is maintained in said bed in aposition whereby stability of said wave is at least in part maintainedby a mechanism of inner-body surface radiation from insulation and/orsaid materials in said matrix, by thermal conduction through the solidportion of the matrix and/or matrix elements, or by forced convectionbetween said matrix and said incoming gases and/or vapors, air and/oroxygen.
 72. A method according to claim 1, wherein the gaseous reactantsare admitted to said matrix through a series of inlet ports, spaced atregular or irregular intervals along the flow axis, to govern theoverall rate of reaction in the matrix.
 73. A method according to claim1, wherein the mechanical integrity of said matrix is maintained by agas-permeable membrane.
 74. A method according to claim 2, wherein thegaseous products of said combustion wave contain levels of nitrous oxide(N₂ O) which do not exceed 0.3 parts per million by volume.
 75. A methodaccording to claim 1, wherein said matrix comprises an interface formedby selecting said heat-resistant matter such that the mean freeradiative path in said matrix, or the emissivity of said matter, or theshape of said matter, or the surface area per unit volume of saidmatter, or the bed particle size of particles comprising said matrix, orthe thermal conductivity of said matter, or the point to point surfacecontact area of particles comprising said matrix, or the void fractionon respective sides of said interface are different from each other. 76.A method according to claim 1, wherein the freeflow area of the matrixis varied, through changes in matrix void fraction or geometriccross-sectional area, along the flow axis to provide for a range ofinlet gas flowrates concurrent with a single matrix burning velocity.77. An apparatus for controlled reaction of gases and/or vapors in astable reaction wave comprisinga. a matrix of solid heat-resistantmatter; b. means for introducing gases and/or vapors into said matrix;c. means for mixing air and/or oxygen with said gases and/or vapors; d.means for controlling the volume and/or flowrate of said gases and/orvapors, air and/or oxygen into said matrix; e. means for monitoring thetemperature in said matrix, f. means for adjusting said flowrate and/orvolume in response to temperature changes in said matrix; g. means forexhausting gases from said matrix.
 78. An apparatus according to claim77 wherein said matrix insulated to retain heat within said bed.
 79. Anapparatus according to claim 77 further comprising a plenum for mixtureof said vapors, gases, oxygen and/or air before introduction into saidmatrix.
 80. An apparatus according to claim 77 wherein saidheat-resistant material comprises a ceramic.
 81. An apparatus accordingto claim 77 further comprising means for preheating said matrix and/orincoming gases prior to introduction of said gases and/or vapors intosaid matrix.
 82. A apparatus according to claim 77 wherein saidheat-resistant matter in said matrix comprises objects of sizes selectedto obtain a predetermined mean-free radiative path in said matrix.
 83. Aapparatus according to claim 77, wherein the emissivity of said matterin said matrix varies to obtain a predetermined back heat transfercharacteristic from solids comprising said matter back into a reactionwave in said matrix.
 84. An apparatus according to claim 79 wherein saidplenum comprises one or more layers of random packing material.
 85. Anapparatus according to claim 84 wherein said layers are configured toachieve a pressure drop across the interfaces between layers.
 86. Anapparatus according to claim 77 wherein said matrix comprises randompacking.
 87. An apparatus according to claim 86 wherein said randompacking comprises ceramic balls.
 88. An apparatus according to claim 87wherein said balls are from 1/16" to 3" in diameter.
 89. An apparatusaccording to claim 88 wherein said balls are about 3/4" in diameter. 90.An apparatus according to claim 86 wherein said random packing comprisesceramic saddles.
 91. An apparatus according to claim 90 wherein saidsaddles are from 1/16" to 3" nominal size.
 92. An apparatus according toclaim 91 wherein said saddles are 1/2" to 1.5" nominal size.
 93. Anapparatus according to claim 77 wherein said matrix comprises structuredceramic packing.
 94. An apparatus according to claim 77 wherein saidmatrix comprises a ceramic foam material.
 95. An apparatus according toclaim 94 wherein said ceramic foam material has a void fraction of 10 to99%.
 96. An apparatus according to claim 95 wherein said ceramic foammaterial has a void fraction of 75 to 95%.
 97. An apparatus according toclaim 96 wherein said ceramic foam material has a void fraction of about90%.
 98. An apparatus according to claim 94 wherein said ceramic foammaterial has a pore size of 0.1 to 1000 pores per inch.
 99. An apparatusaccording to claim 98 wherein said ceramic foam material has a pore sizeof 5 to 100 pores per inch.
 100. An apparatus according to claim 99wherein said ceramic foam material has a pore size of about 10 to 30pores per inch.
 101. An apparatus according to claim 80 wherein saidceramic matrix comprises a ceramic honeycomb shaped material.
 102. Anapparatus according to claim 77 wherein said heat-resistant mattercomprises a metal matrix.
 103. An apparatus according to claim 102wherein said metal matrix comprises random metal packing.
 104. Anapparatus according to claim 102 wherein said metal matrix comprisesstructured metal packing.
 105. An apparatus according to claim 81wherein said preheating means comprises a pre-heating burner.
 106. Anapparatus according to claim 81 wherein said preheating means comprisesan electric heater.
 107. An apparatus according to claim 77, whereinsaid means for introducing gases comprises inlet ports, spaced atregular or irregular intervals along the flow axis, to govern theoverall rate of reaction in said matrix.
 108. An apparatus according toclaim 77, further comprising a gas permeable membrane to maintain themechanical integrity of said matrix.